Regarding manufacturer data, I live by the Russian proverb "trust, but verify". IWC says the power reserve of the 3239 is "42 hours when fully wound". I just measured it, and it took most of my willpower to leave that barely week-old watch undisturbed for so long, but what wouldn't I do for the enlightenment of fellow forum members? It's not 42 hours. It's 51.